High-temperature spin-on temporary bonding compositions

ABSTRACT

New compositions and methods of using those compositions as bonding compositions are provided. The compositions are preferably thermoplastic and comprise imides, amideimides, and/or amideimide-siloxanes (either in polymeric or oligomeric form) dispersed or dissolved in a solvent system, and can be used to bond an active wafer to a carrier wafer or substrate to assist in protecting the active wafer and its active sites during subsequent processing and handling. The compositions form bonding layers that are chemically and thermally resistant, but that can also be softened to allow the wafers to slide apart at the appropriate stage in the fabrication process.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/146,148, entitled HIGH-TEMPERATURE SPIN-ON TEMPORARY BONDINGCOMPOSITIONS, filed Jun. 25, 2008, which claims the priority benefit ofU.S. Provisional Patent Application Ser. No. 60/946,077, entitledHIGH-TEMPERATURE SPIN-ON BONDING COMPOSITIONS FOR TEMPORARY WAFERBONDING USING SLIDING APPROACH, filed Jun. 25, 2007, each of which isincorporated by reference herein.

GOVERNMENT FUNDING

This invention was made with government support under contract numberW911 SR-05-C-0019 awarded by the United States Army Research,Development, and Engineering Command. The United States Government hascertain rights in the invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is broadly concerned with novel compositions andmethods of using those compositions to form bonding compositions thatcan support active wafers on a carrier wafer or substrate during waferthinning and other processing.

2. Description of the Prior Art

Wafer (substrate) thinning has been used to dissipate heat and aid inthe electrical operation of the integrated circuits (IC). Thicksubstrates cause an increase in capacitance, requiring thickertransmission lines, and, in turn, a larger IC footprint. Substratethinning increases impedance while capacitance decreases impedance,causing a reduction in transmission line thickness, and, in turn, areduction in IC size. Thus, substrate thinning facilitates ICminiaturization.

Geometrical limitations are an additional incentive for substratethinning. Via holes are etched on the backside of a substrate tofacilitate frontside contacts. In order to construct a via using commondry-etch techniques, geometric restrictions apply. For substratethicknesses of less than 100 μm, a via having a diameter of 30-70 μm isconstructed using dry-etch methods that produce minimal post-etchresidue within an acceptable time. For thick substrates, vias withlarger diameters are needed. This requires longer dry-etch times andproduces larger quantities of post-etch residue, thus significantlyreducing throughput. Larger vias also require larger quantities ofmetallization, which is more costly. Therefore, for backside processing,thin substrates can be processed more quickly and at lower cost.

Thin substrates are also more easily cut and scribed into ICs. Thinnersubstrates have a smaller amount of material to penetrate and cut andtherefore require less effort. No matter what method (sawing, scribe andbreak, or laser ablation) is used, ICs are easier to cut from thinnersubstrates. Most semiconductor wafers are thinned after frontsideoperations. For ease of handling, wafers are processed (i.e., frontsidedevices) at their normal full-size thicknesses, e.g., 600-700 μm. Oncecompleted, they are thinned to thicknesses of 100-150 μm. In some cases(e.g., when hybrid substrates such as gallium arsenide (GaAs) are usedfor high-power devices) thicknesses may be taken down to 25 μm.

Mechanical substrate thinning is performed by bringing the wafer surfaceinto contact with a hard and flat rotating horizontal platter thatcontains a liquid slurry. The slurry may contain abrasive media alongwith chemical etchants such as ammonia, fluoride, or combinationsthereof. The abrasive provides “gross” substrate removal, i.e.,thinning, while the etchant chemistry facilitates “polishing” at thesubmicron level. The wafer is maintained in contact with the media untilan amount of substrate has been removed to achieve a targeted thickness.

For a wafer thickness of 300 μm or greater, the wafer is held in placewith tooling that utilizes a vacuum chuck or some means of mechanicalattachment. When wafer thickness is reduced to less than 300 μm, itbecomes difficult or impossible to maintain control with regard toattachment and handling of the wafer during further thinning andprocessing. In some cases, mechanical devices may be made to attach andhold onto thinned wafers, however, they are subject to many problems,especially when processes may vary. For this reason, the wafers(“active” wafers) are mounted onto a separate rigid (carrier) substrateor wafer. This substrate becomes the holding platform for furtherthinning and post-thinning processing. Carrier substrates are composedof materials such as sapphire, quartz, certain glasses, and silicon, andusually exhibit a thickness of 1000 μm. Substrate choice will depend onhow closely matched the coefficient of thermal expansion (CTE) isbetween each material.

One method that has been used to mount an active wafer to a carriersubstrate comprises the use of a cured bonding composition. The majordrawback with this approach is that the composition must be chemicallyremoved, typically by dissolving in a solvent. This is verytime-consuming, thus reducing throughput. Furthermore, the use of thesolvent adds to the cost and complexity of the process, and it can behazardous, depending upon the solvent required to dissolve the bondingcomposition.

Another method for mounting an active wafer to a carrier substrate isvia a thermal release adhesive tape. This process has two majorshortcomings. First, the tapes have limited thickness uniformity acrossthe active wafer/carrier substrate interface, and this limiteduniformity is often inadequate for ultra-thin wafer handling. Second,the thermal release adhesive softens at such low temperatures that thebonded wafer/carrier substrate stack cannot withstand many typical waferprocessing steps that are carried out at higher temperatures.

There is a need for new compositions and methods of adhering an activewafer to a carrier substrate that can endure high processingtemperatures and that allow for ready separation of the wafer andsubstrate at the appropriate stage of the process.

SUMMARY OF THE INVENTION

The present invention overcomes the problems of the prior art by broadlyproviding a wafer bonding method which includes providing a stackcomprising first and second substrates bonded together via a bondingcomposition layer. The layer comprises a compound that can be oligomericor polymeric, and that is selected from the group consisting of imide,amideimide, and amideimide-siloxane polymers and oligomers. The stack issubjected to a temperature sufficiently high to soften the bondinglayer, and then the first and second substrates are separated.

The invention also provides an article comprising first and secondsubstrates. The first substrate comprises a back surface and an activesurface, and the active surface comprises at least one active site and aplurality of topographical features. The second substrate has a bondingsurface, and there is a bonding layer bonded to the active surface andto the bonding surface. The bonding layer comprises oligomers andpolymers, which are selected from the group consisting of imide,amideimide, and amideimide-siloxane polymers and oligomers.

In a further embodiment, the invention is concerned with a polymer oroligomer (or compositions comprising this polymer or oligomer dissolvedor dispersed in a solvent system) having a formula selected from thegroup consisting of

wherein:

R is selected from the group consisting of

-   -   wherein R₁ is selected from the group consisting of        alkyl-substituted phenyls,

-   -    and

X is selected from the group consisting of phenyl sulfones, aromatics,aliphatics, and cyclic aliphatics; and

where Z is selected from the group consisting of siloxanes and moietiescomprising ether bridges. The compound further comprises an endcap groupderived from a compound selected from the group consisting of aromaticmono-amines, aliphatic mono-amines, cyclo-aliphatic mono-amines, andphthalic anhydrides.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the inventive method of thinning and debonding twowafers according to the present invention;

FIG. 2 is a flow diagram showing the typical process steps followed inthe examples; and

FIG. 3 is a graph depicting the rheological analysis results of abonding composition according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In more detail, the inventive compositions comprise a compound dispersedor dissolved in a solvent system. The compound can be a polymer or anoligomer and is preferably present in the composition at levels of fromabout 1% to about 70% by weight, more preferably from about 5% to about50% by weight, and even more preferably from about 15% to about 40% byweight, based upon the total weight of solids in the composition takenas 100% by weight.

The preferred polymeric or oligomeric compounds are thermoplastic andpreferably have a weight average molecular weight of from about 3,000Daltons to about 300,000 Daltons, and more preferably from about 6,000Daltons to about 50,000 Daltons. Preferred compounds preferably have asoftening temperature (melt viscosity at 3,000 Pa·S) of at least about150° C., more preferably at least about 200° C., and even morepreferably from about 200° C. to about 250° C.

Preferred compounds will be at least about 95%, preferably at leastabout 98%, and even more preferably about 100% by weight dissolved whenallowed to sit at ambient temperatures in a solvent such asN-methyl-2-pyrrolidone, xylene, dimethylacetamide,N,N-dimethylformamide, dimethyl sulfoxide, and mixtures thereof, for atime period of about 1-24 hours.

Some preferred compounds that work in the present invention includethose selected from the group consisting of oligomers and polymers ofimides, amideimides, amideimide-siloxanes, and mixtures thereof.

In one embodiment, preferred such compounds have the formula

where R is selected from the group consisting of

where R₁ is selected from the group consisting of alkyl-substitutedphenyls,

Preferred alkyl-substituted phenyls for use in the present invention arephenyls substituted with C₁ to C₆ alkyls. Particularly preferredexamples of alkyl-substituted phenyls are those selected from the groupconsisting of

In formula (I) above, X is selected from the group consisting of phenylsulfones, aromatics (preferably C₆ to C₆₀, more preferably C₆ to C₃₀,and even more preferably C₆ to C₂₄), aliphatics (preferably C₂ to C₁₅,more preferably C₂ to C₁₀, and even more preferably C₂-C₆), and cyclicaliphatics (preferably C₄ to C₆₀, more preferably C₄ to C₂₀, and evenmore preferably C₄-C₁₂).

In one embodiment, X can be the above aromatic group, aliphatic group,or cyclic aliphatic group. In another embodiment, X can comprisearomatic groups with ether bridges (such as those discussed with respectto Z below) or aromatic groups with linkage groups and/or —NH₂ groups atthe meta position.

Particularly preferred X groups are selected from the group consistingof alkyl substituted phenyls (such as the ones discussed above),isopropylidenediphenyl, and hexafluoroisopropylidene.

In another embodiment, preferred such compounds have the formula

where Z is selected from the group consisting of siloxanes and moietiescomprising ether bridges. In embodiments where Z is a siloxane,preferred siloxanes have the formula

where:

-   -   each R³ is individually selected from the group consisting of        hydrogen, alkyls (preferably C₁ to C₁₀, and more preferably        C₁-C₂), and phenyls;    -   m is 1 to 6; and    -   p is 1 to 50, preferably 1 to 20, and more preferably 1 to 10.

Preferred moieties comprising ether bridges are selected from the groupconsisting of

In either the embodiment of Formula (I) or the embodiment of Formula(II), it is preferred that the polymer or oligomer further comprise anendcap group. Preferred endcap groups are derived from a compoundselected from the group consisting of aromatic mono-amines, aliphaticmono-amines, cyclo-aliphatic mono-amines, and phthalic anhydrides.Particularly preferred endcap groups have a formula selected from thegroup consisting of alkyls (preferably C₁ to C₁₅, more preferably C₁ toC₁₀, and even more preferably C₁-C₆),

where:

R₄ is an alkyl group (preferably C₁ to C₁₅, more preferably C₁ to C₁₀,and even more preferably C₁-C₆);

R₅ is a cyclic aliphatic group (preferably C₃ to C₁₂, and morepreferably C₅ to C₆); and

k is 0 to 20, preferably 0 to 10, and more preferably 0 to 5.

The composition should comprise at least about 30% by weight solventsystem, preferably from about 50% to about 90% by weight solvent system,more preferably from about 60% to about 90% by weight solvent system,and even more preferably from about 70% to about 90% by weight solventsystem, based upon the total weight of the composition taken as 100% byweight. The solvent system should have a boiling point of from about100-250° C., and preferably from about 120-220° C.

Suitable solvents include those selected from the group consisting ofN-methyl-2-pyrrolidone, xylene, dimethylacetamide,N,N-dimethylformamide, dimethyl sulfoxide, and mixtures thereof.

The total solids level in the composition should be at least about 10%by weight, preferably from about 10% to about 40% by weight, and morepreferably from about 10% to about 30% by weight, based upon the totalweight of the composition taken as 100% by weight.

In other embodiments, the composition could include a number of optionalingredients, including surfactants, adhesion promoting agents,plasticizers, and/or antioxidants.

When a surfactant is utilized, it is preferably present in thecomposition at a level of from about 0.1% to about 3% by weight, andmore preferably from about 0.1% to about 1% by weight, based upon thetotal weight of the solids in the composition taken as 100% by weight.Examples of suitable surfactants include alcohol ethoxylates such asoctyl phenol ethoxylate (sold under the name Triton® X-100).

When an adhesion promoting agent is utilized, it is preferably presentin the composition at a level of from about 0.1% to about 3% by weight,and preferably from about 0.1% to about 1% by weight, based upon thetotal weight of the solids in the composition taken as 100% by weight.Examples of suitable adhesion promoting agent include those selectedfrom the group consisting of bis(trimethoxysilylethyl)benzene,aminopropyl tri(alkoxy silanes) (e.g., aminopropyl tri(methoxy silane),aminopropyl tri(ethoxy silanes), -phenyl aminopropyl tri(ethoxysilane)), and other silane coupling agents.

When an antioxidant is utilized, it is preferably present in thecomposition at a level of from about 0.01% to about 3% by weight, morepreferably from about 0.01% to about 1.5% by weight, and even morepreferably from about 0.01% to about 0.1% by weight, based upon thetotal weight of the solids in the composition taken as 100% by weight.Examples of suitable antioxidants include those selected from the groupconsisting of phenolic antioxidants (such as pentaerythritoltetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate sold under thename Irganox® 1010 by Ciba) and phosphite antioxidants (such astris(2,4-ditert-butylphenyl)phosphite sold under the name Irgafos® 168by Ciba).

The above ingredients can simply be mixed with the compound in thesolvent system. The final composition should be thermoplastic (i.e.,noncrosslinkable). Thus, the composition will be essentially free (lessthan about 0.1% by weight and preferably about 0% by weight) ofcrosslinking agents.

The melt viscosity of the final composition will preferably be less thanabout 200 Pa·S, more preferably less than about 100 Pa·S, and even morepreferably from about 10 Pa·S to about 50 Pa·S. For purposes of thesemeasurements, the melt viscosity is determined via rheological dynamicanalysis (TA Instruments, AR-2000, two parallel-plate configurationwhere the plates have a diameter of 25 mm). Furthermore, this meltviscosity is determined at 300-350° C. and there is preferably less thanabout 3% by weight, and more preferably less than about 2% by weight,loss of the composition. In other words, very little to no thermaldecomposition occurs in the composition at this temperature, asdetermined by thermogravimetric analysis (TGA).

Although the composition could be applied to either the carriersubstrate or active wafer first, it is preferred that it be applied tothe active wafer first. A preferred application method involvesspin-coating the composition at spin speeds of from about 300-3,500 rpm(more preferably from about 500-1,500 rpm), at accelerations of fromabout 500-15,000 rpm/second, and for spin times of from about 30-300seconds. It will be appreciated that the application steps can be variedto achieve a particular thickness.

After coating, the substrate can be baked (e.g., on a hot plate) toevaporate the solvents. Typical baking would be at temperatures of fromabout 80-275° C., and preferably from about 150-225° C. for a timeperiod of from about 2-15 minutes, and more preferably from about 3-10minutes. The film thickness (on top of the topography) after bake willtypically be at least about 5 μm, and more preferably from about 5-50μm.

After baking, the desired carrier wafer is contacted with, and pressedagainst, the layer of inventive composition. The carrier wafer is bondedto this inventive composition by heating at a temperature of from about150-300° C., and preferably from about 180-300° C. This heating ispreferably carried out under vacuum and for a time period of from about1-10 minutes, under a bond force of from about 1 to about 15kilonewtons.

FIG. 1( a) shows an exemplary stack 10 comprising active wafer 12 andcarrier wafer or substrate 14. Active wafer 12 comprises a back surface16 and an active surface 18. Active surface 18 can comprise one or moreactive sites (not shown) as well as a plurality of topographicalfeatures (raised features or lines as well as holes, trenches, orspaces) such as, for example, those designated as 20 a-d. Feature 20 drepresents the “highest” feature on active surface 18. That is, the endportion or surface 21 is further from back surface 16 of wafer 12 thanthe respective end portions of any other topographical feature on wafer12.

Typical active wafers 12 can include any microelectronic substrate.Examples of some possible active wafers 12 include those selected fromthe group consisting of microelectromechanical system (MEMS) devices,display devices, flexible substrates (e.g., cured epoxy substrates,roll-up substrates that can be used to form maps), compoundsemiconductors, low k dielectric layers, dielectric layers (e.g.,silicon oxide, silicon nitride), ion implant layers, and substratescomprising silicon, aluminum, tungsten, tungsten silicide, galliumarsenide, germanium, tantalum, tantalum nitrite, SiGe, and mixtures ofthe foregoing.

Carrier substrate 14 has a bonding surface 22. Typical carriersubstrates 14 comprise a material selected from the group consisting ofsapphire, ceramic, glass, quartz, aluminum, silver, and silicon.

Wafer 12 and carrier substrate 14 are bonded together via bondingcomposition layer 24. Bonding layer 24 is formed of the polymercompositions described above, and has been applied and dried as alsodescribed above. As shown in the FIG. 1( a), bonding layer 24 is bondedto active surface 18 of wafer 12 as well as to bonding surface 22 ofsubstrate 14. Unlike prior art tapes, bonding layer 24 is a uniform(chemically the same) material across its thickness. In other words, theentire bonding layer 24 is formed of the same composition.

It will be appreciated that, because bonding layer 24 can be applied toactive surface 18 by spin-coating, the bonding composition flows intoand over the various topographical features. Furthermore, the bondinglayer 24 forms a uniform layer over the topography of active surface 18.To illustrate this point, FIG. 1 shows a plane designated by dashed line26, at end portion 21 and substantially parallel to back surface 16. Thedistance from this plane to bonding surface 22 is represented by thethickness “T.” The thickness “T” will vary by less than about 8%,preferably by less than about 5%, more preferably by less than about 2%,and even more preferably by less than about 1% across the length ofplane 26 and substrate 14.

The wafer package can then be subjected to subsequent thinning (or otherprocessing) of the substrate as shown in FIG. 1( b), where 12′ presentsthe wafer 12 after thinning. It will be appreciated that the substratescan be thinned to thicknesses of less than about 100 μm, preferably lessthan about 50 μm, and more preferably less than about 25 μm. Afterthinning, typical backside processing, including photolithography, viaetching, and metallization, may be performed.

Advantageously, the dried layers of the inventive compositions possess anumber of highly desirable properties. For example, the layers willexhibit low outgassing for vacuum etch processes. That is, if a 15-μmthick film of the composition is baked at 200° C. for 2 minutes, thesolvents will be driven from the composition so that subsequent bakingat 200° C. for 60 minutes results in a film thickness change of lessthan about 5%, preferably less than about 2%, and even more preferablyless than about 1% or even 0% (referred to as the “Film ShrinkageTest”). Thus, the dried layers can be heated to temperatures of up toabout 190° C., preferably up to about 200° C., more preferably up toabout 220° C., and even more preferably up to about 240° C. withoutphysical changes or chemical reactions occurring in the layer. Forexample, the layers will not soften below these temperatures. In someembodiments, the layers can also be exposed to polar solvents (e.g.,PGME) at a temperature of 85° C. for 90 minutes without reacting.

The bond integrity of the dried layers can be maintained even uponexposure to an acid or base. That is, a dried layer of the compositionhaving a thickness of about 15 μm can be submerged in an acidic media(e.g., concentrated sulfuric acid) or base (e.g., 30 wt. % KOH) at 85°C. for about 45 minutes while maintaining bond integrity. Bond integritycan be evaluated by using a glass carrier substrate and visuallyobserving the bonding composition layer through the glass carriersubstrate to check for bubbles, voids, etc. Also, bond integrity ismaintained if the active wafer and carrier substrate cannot be separatedby hand.

After the desired processing has occurred, the active wafer or substratecan be separated from the carrier substrate by heating to temperaturesof at least about 200° C., preferably at least about 225° C., and morepreferably from about 250° C. to about 350° C. These temperature rangesrepresent the preferred softening points of the bonding compositionlayer. This heating will cause the bonding composition layer to softenand form softened bonding composition layer 24′ as shown in FIG. 1( c),at which point the two substrates can be separated by sliding apart.FIG. 1( c) also shows an axis 28, which passes through both of wafer 12and substrate 14, and the sliding forces would be applied in a directiongenerally transverse to axis 28. Alternatively, sliding may not benecessary, and instead wafer 12 or substrate 14 can be lifted upward(i.e., in a direction that is generally away from the other of wafer 12or substrate 14) to separate the wafer 12 from the substrate 14.

It will be appreciated that separation can be accomplished by simplysliding and/or lifting one of wafer 12 or substrate 14 while maintainingthe other in a substantially stationary position so as to resist thesliding or lifting force (e.g., by applying simultaneous opposingsliding forces to wafer 12 and substrate 14). This can all beaccomplished via conventional equipment.

Any bonding composition remaining in the device areas can be easilyremoved using the original solvent that was part of the compositionprior to drying as well as using solvents such as xylene, NMP, anddimethyl sulfoxide. Any composition remaining behind will be completelydissolved (at least about 98%, preferably at least about 99%, and morepreferably about 100%) after 5-15 minutes of exposure to the solvent. Itis also acceptable to remove any remaining bonding composition using aplasma etch, either alone or in combination with a solvent removalprocess. After this step, a clean, bonding composition-free wafer 12′and carrier substrate 14 (not shown in their clean state) will remain.

EXAMPLES

The following examples set forth preferred methods in accordance withthe invention. It is to be understood, however, that these examples areprovided by way of illustration and nothing therein should be taken as alimitation upon the overall scope of the invention.

Example 1 Bisphenol-A-Dianhydride-co-1,3-Phenylenediamine OligomersEnd-Terminated with 2,6-Dimethyl Aniline

In this procedure, 4,4′-bisphenol-A-dianhydride (BPADA, 57.25 grams,0.011 moles), m-phenylene diamine (10.81 grams, 0.01 mol), and2,6-dimethyl aniline (2.42 grams, 0.02 mol) were dissolved inN-methyl-2-pyrrolidone up to a final concentration of 15 wt. % of BPADA.The solution was allowed to stir at room temperature under an inertatmosphere for 12 hours. Xylene (38.17 grams) was added to the resultingamic acid solution to form an azeotropic solution to remove water duringimidization, carried out by heating the solution to 180° C. for anadditional 12 hours. The resulting imide solution was spin coated at1,500 rpm for 60 seconds to form void-free, homogeneous films.

Example 2 Bisphenol-A-Dianhydride-co-1,3-Phenylenediamine OligomersEnd-Terminated with n-Butyl Amine

In this Example, 4,4′-bisphenol-A-dianhydride (57.25 grams, 0.011moles), m-phenylene diamine (10.81 grams, 0.01 mol), and n-butyl amine(1.46 grams, 0.02 mol) were dissolved in N-methyl-2-pyrrolidone up to afinal concentration of 15 wt. % of BPADA. The solution was allowed tostir at room temperature under an inert atmosphere for 12 hours. Afterthis stage, the resulting poly(amic-acid) solution, with added xylene(38.17 grams), was imidized upon heating to 180° C. under a nitrogenpurge for additional 12 hours.

Example 3 Bisphenol-A-Dianhydride-co-O-Tolidine Oligomers End-Terminatedwith 2,6-Dimethyl Aniline

For this procedure, 4,4′-Bisphenol-A-dianhydride (57.25 grams, 0.011moles), O-Tolidine (21.229 grams, 0.01 mol), and 2,6-dimethyl aniline(2.42 grams, 0.02 mol) were dissolved in N-methyl-2-pyrrolidone up to afinal concentration of 15 wt % of BPADA. The solution was allowed tostir at room temperature under an inert atmosphere for 12 hours. Xylene(38.17 grams) was added to the resulting amic acid solution to form anazeotropic solution to remove water during imidization, carried out byheating the solution to 180° C. for an additional 12 hours. Theresulting imide solution was spin coated at appropriate speed to formvoid-free, homogeneous films.

Example 4Bisphenol-A-Dianhydride-co-1,3-Phenylenediamine-co-2-Methyl-1,5-PentanediamineOligomers End-Terminated with 2,6-Dimethyl Aniline

In this example, 4,4′-bisphenol-A-dianhydride (57.25 grams, 0.011moles), m-phenylene diamine (7.57 grams, 0.007 mol),2-methyl-1,5-pentanediamine (0.348 grams, 0.003 mol, commerciallyavailable from Invista under trade name of DYTEK-A), and 2,6-dimethylaniline (2.42 grams, 0.02 mol) were dissolved in N-methyl-2-pyrrolidoneup to a final concentration of 15 wt. % of BPADA. The solution wasallowed to stir at room temperature under an inert atmosphere for 12hours. Xylene (38.17 grams) was added to the resulting amic acidsolution to form an azeotropic solution to remove water duringimidization, carried out by heating the solution to 180° C. for anadditional 12 hours. The resulting imide solution was spin coated atappropriate speed to form void-free, homogeneous films.

Example 5 Trimellitic Anhydride Chloride-co-2,2-Bis[4-(4-aminophenoxy)Phenyl] Propane-co-Bisphenol A-Dianhydride Oligomers End-Terminated withPhthalic Anhydride

In this procedure, trimellitic anhydride chloride (0.447 grams, 2.12mmol), 2,2-bis[4-(4-aminophenoxy)phenyl] propane (2.0 grams, 4.87 mmol),and triethylamine (0.257 grams, 2.54 mmol) were dissolved inN-methyl-2-pyrrolidone at 0-5° C. to a concentration of 15 wt. % of thetotal amount of all monomers. The solution was allowed to stir at 0-5°C. under an inert atmosphere for 2 hours. Next,4,4′-bisphenol-A-dianhydride (1.105 grams, 2.12 mmol), phthalicanhydride (0.199 grams, 1.34 mmol), and additionalN-methyl-2-pyrrolidone were added to a final concentration of 15 wt. %.The solution was stirred at room temperature under an inert atmospherefor 20 hours. The resulting precipitate (triethylamine chloride) wasfiltered, and xylene (2.5 grams) was added to the amic-acid solution toform an azeotropic solution to remove water during imidization, whichwas carried out by heating the solution to 180° C. for an additional 12hours. The structure of the polymer is shown below. The resultingamide-imide solution was spin coated at appropriate speed to formvoid-free, homogeneous films.

Example 6 Trimellitic Anhydride Chloride-co-2,2-Bis[4-(4-Aminophenoxy)Phenyl] Propane Oligomers End-Terminated with Phthalic Anhydride

In this Example, trimellitic anhydride chloride (1.0 grams, 4.7 mmol),2,2-Bis[4-(4-aminophenoxy)phenyl] propane (2.464 grams, 6.0 mmol), andtriethylamine (0.571 grams, 5.64 mmol) were dissolved inN-methyl-2-pyrrolidone at 0-5° C. to a concentration of 15 wt. %. Thesolution was allowed to stir at 0-5° C. under an inert atmosphere for 1hour. Phthalic anhydride (0.439 grams, 2.96 mmol) and additionalN-methyl-2-pyrrolidone were added to a final concentration of 15 wt. %.The solution was stirred at room temperature under an inert atmospherefor 20 hours. The resulting precipitate (triethylamine chloride) wasfiltered, and xylene (2.6 grams) was added to the amic-acid solution toform an azeotropic solution to remove water during imidization, whichwas carried out by heating the solution to 180° C. for additional 12hours. The resulting amide-imide solution was spin coated at appropriatespeed to form void-free, homogeneous films.

Example 7 Trimellitic Anhydride Chloride-co-1,3-Bis(3-Aminophenoxy)Benzene Oligomers End-Terminated with Phthalic Anhydride

In this procedure, trimellitic anhydride chloride (0.69 grams, 3.28mmol), 1,3-Bis(3-aminophenoxy)benzene (Commercially available fromCHRISKEV Company, Inc. under trade name of APB-133, 1.0 grams, 3.42mmol), and triethylamine (0.398 grams, 3.93 mmol) were dissolved inN-methyl-2-pyrrolidone at 0-5° C. to a concentration of 15 wt. %. Thesolution was allowed to stir at 0-5° C. under an inert atmosphere for 1hour. Phthalic anhydride (0.0427 grams, 0.29 mmol) and additionalN-methyl-2-pyrrolidone were added to a final concentration of 15 wt. %.The solution was stirred at room temperature under an inert atmospherefor 20 hours. The resulting precipitate (triethylamine chloride) wasfiltered, and xylene (1.29 grams) was added to the amic-acid solution toform an azeotropic solution to remove water during imidization, carriedout by heating the solution to 180° C. for an additional 12 hours. Theresulting amide-imide solution was spin coated at appropriate speed toform void-free, homogeneous films.

Example 8 Amide Capped Disiloxane-co-2,2-Bis[4-(4-Aminophenoxy)phenyl]propane-co-Trimellitic Anhydride Chloride Oligomers End-Terminated withPhthalic Anhydride

In this procedure, trimellitic anhydride chloride (1.149 grams, 5.46mmol), 1,3-bis(3-aminopropyl) tetramethyl disiloxane (0.226 grams, 0.91mmol), and triethylamine (0.663 grams, 6.55 mmol) were dissolved inN-methyl-2-pyrrolidone/THF cosolvent (70/30 vol) at 0-5° C. to aconcentration of 15 wt. %. The solution was allowed to stir at 0-5° C.under an inert atmosphere for 12 hours. Next,2,2-Bis[4-(4-aminophenoxy)phenyl] propane (2.0 grams, 4.87 mmol),phthalic anhydride (0.108 grams, 0.729 mmol), and additionalN-methyl-2-pyrrolidone were added to a final concentration of 15 wt. %.The solution was stirred at room temperature under an inert atmospherefor 12 hours. The resulting precipitate (triethylamine chloride) wasfiltered, and xylene (2.3 grams) was added to the amic-acid solution toform an azeotropic solution to remove water during imidization, whichwas carried out by heating the solution to 180° C. for an additional 12hours. The resulting amide-imide-siloxane solution was spin coated at1,500 rpm for 60 seconds to form void-free, homogeneous films.

Example 9 Amide Capped Disiloxane-co-2,2-Bis[4-(4-Aminophenoxy)phenyl]propane-co-Bisphenol-A-Dianhydride Oligomers End-Terminated withPhthalic Anhydride

In this procedure, trimellitic anhydride chloride (0.372 grams, 1.77mmol), 1,3-bis(3-aminopropyl) tetramethyl disiloxane (0.220 grams, 0.89mmol), and triethylamine (0.215 grams, 2.12 mmol) were dissolved inN-methyl-2-pyrrolidone/THF cosolvent (70/30 vol) at 0-5° C. to aconcentration of 15 wt. %. The solution was allowed to stir at 0-5° C.under an inert atmosphere for 12 hours. Next,2,2-Bis[4-(4-aminophenoxy)phenyl] propane (2.0 grams, 4.87 mmol),4,4′-Bisphenol-A-dianhydride (1.840 grams, 3.54 mmol), phthalicanhydride (0.141 grams, 0.95 mmol), and additionalN-methyl-2-pyrrolidone were added to a final concentration of 15 wt. %.The solution was stirred at room temperature under an inert atmospherefor 12 hours. The resulting precipitate (triethylamine chloride) wasfiltered, and xylene (3.0 grams) was added to the amic-acid solution toform an azeotropic solution to remove water during imidization, whichwas carried out by heating the solution to 180° C. for an additional 12hours. The resulting amide-imide-siloxane solution was spin coated at1,500 rpm for 60 seconds to form void-free, homogeneous films.

Example 10 Amide CappedPolydisiloxane-co-2,2-Bis[4-(4-Aminophenoxy)phenyl]propane-co-Trimellitic Anhydride Chloride Oligomers End-Terminated withPhthalic Anhydride

In this Example, trimellitic anhydride chloride (1.080 grams, 5.13mmol), aminopropyl terminated polydimethylsiloxane (commerciallyavailable from Gelest, Inc., 0.420 grams, 0.47 mmol), and triethylamine(0.623 grams, 6.15 mmol) were dissolved in N-methyl-2-pyrrolidone/THFcosolvent (70/30 vol) at 0-5° C. to a concentration of 15 wt. %. Thesolution was allowed to stir at 0-5° C. under an inert atmosphere for 12hours. Next, 2,2-Bis[4-(4-aminophenoxy)phenyl] propane (2.0 grams, 4.87mmol), phthalic anhydride (0.063 grams, 0.425 mmol), and additionalN-methyl-2-pyrrolidone were added to a final concentration of 15 wt. %.The solution was stirred at room temperature under an inert atmospherefor 12 hours. The resulting precipitate (triethylamine chloride) wasfiltered, and xylene (2.4 grams) was added to the amic-acid solution toform an azeotropic solution to remove water during imidization, whichwas carried out by heating the solution to 180° C. for additional 12hours. The resulting amide-imide-siloxane solution was spin coated at1,500 rpm for 60 seconds to form void-free, homogeneous films.

Example 11 Application, Bonding, and Debonding

The formulations from Examples 1 through 10 were spin-coated ontovarious substrate wafers. After baking to evaporate the solvent, asecond wafer was bonded to each coated wafer by applying pressure. Thetypical procedure for temporary wafer bonding using these adhesives isshown in FIG. 2. The bonded wafers were tested for mechanical strength,thermal stability, and chemical resistance. The wafers were tested forde-bonding by manually sliding them apart at acceptable temperatures.

Example 12 Analysis of the Adhesives—Polyimides

The viscosity, softening point, and T_(g) of the compositions ofExamples 1 and 3 are reported in Table 1, and all these materials weresuccessfully tested for de-bonding. Further studies on thermal stabilityand chemical resistance were carried out on these four compositions. Allof these compositions possessed the required thermal stability of atleast up to 350° C. and exhibited minimal out-gassing (<0.5 wt. %).

TABLE 1 Properties of Examples 1 and 3 VISCOSITY Softening TemperatureMolecular Weight T_(g) EXAMPLE (Pa · S, 350° C.) (in ° C. at 3,000 Pa ·S) (M_(w), Daltons) (° C.) 1 50 210 10,800 161 3 15 210 6,100 152

Example 13 Analysis of the Adhesives—Polyamideimides

The compositions of the amideimide polymers from Examples 5-7 havearomatic amines that have ether or alkane linkages. As a result, thematerials have low softening points, glass transition temperatures, andmelt viscosities. The rheology data of the example materials are shownin FIG. 3. The viscosity, softening point, and T_(g) of the examples arereported in Table 2, and all these materials have been successfullytested for de-bonding. Further studies on thermal stability and chemicalresistance have been carried out on these compositions. All of thesecompositions possess the required thermal stability at least up to 350°C. and exhibit minimal out-gassing (<0.5 wt. %).

TABLE 2 Properties of Examples 5-7 VISCOSITY Softening Weight LossMolecular (Pa · S, Temperature (Isothermal at Weight (M_(n), T_(g)EXAMPLE 350° C.) (in ° C. at 3,000 Pa · S) 350° C. for 4 hrs) Daltons)(° C.) 5 20 253 1.337% 6,000 173 6 112 282 1.561% 3,000 195 7 37 2552.218% 6,000 163

Example 14 Analysis of the Adhesives—Poly(Amideimide-Siloxane)s

The compositions of the amideimide-siloxane polymers from Examples 8-10include siloxane units that are capped by amide groups, which formhydrogen bonding inter- and intra-molecularly. As a result, the siloxaneunits are isolated from phase change and prevented from introducingphase separation. This effect is shown below. The viscosities, softeningpoints, and T_(g) of the examples are reported in Table 3, and all ofthese materials were successfully tested for de-bonding. Further studieson thermal stability and chemical resistance have been carried out onthese compositions. All of these compositions possess the requiredthermal stability at least up to 350° C. and exhibit minimal out-gassing(<0.5 wt. %).

TABLE 3 Properties of Examples 8-10 Weight Loss Molecular VISCOSITYSoftening Temperature (Isothermal at Weight (M_(n), T_(g) EXAMPLE (Pa ·S, 350° C.) (in ° C. at 3,000 Pa · S) 350° C. for 4 hrs) Daltons) (° C.)8 44 260 4.085% 10,000 197 9 67 253 1.407% 10,000 150 10 1017 312 2.293%16,000 150

Example 15 Trimellitic Anhydride Chloride-co-2,2-Bis[4-(3-Aminophenoxy)Phenyl] Sulfone-co-Bisphenol-A-Dianhydride Oligomers End-Terminated withPhthalic Anhydride

Trimellitic anhydride chloride (2.245 grams, 10.66 mmol),2,2-Bis[4-(3-aminophenoxy)phenyl] sulfone (10.0 grams, 23.12 mmol), andtriethylamine (1.294 grams, 12.79 mmol) were dissolved inN-methyl-2-pyrrolidone at 0-5° C. to a concentration of 15 wt. %. Thesolution was allowed to stir at 0-5° C. under an inert atmosphere for 1hour. Bisphenol-A-dianhydride (5.550 grams, 10.66 mmol), phthalicanhydride (0.555 grams, 3.74 mmol), and additionalN-methyl-2-pyrrolidone were added to a final concentration of 15 wt. %.The solution was stirred at room temperature under an inert atmospherefor 20 hours. The resulting precipitate (triethylamine chloride) wasfiltered, and xylene (6.2 grams) was added to the amic-acid solution toform an azeotropic solution to remove water during imidization, carriedout by heating the solution to 180° C. for an additional 12 hours. Theresulting amide-imide solution was spin coated at 1,500 rpm for 60seconds to form void-free, homogeneous films.

Example 16 Bisphenol-A-Dianhydride-co-2,2-Bis[4-(4-Aminophenoxy) Phenyl]Sulfone Oligomers End-Terminated with Cyclohexylamine

In this procedure, 4,4′-Bisphenol-A-dianhydride (10.624 grams, 20.40mmol), 2,2-Bis[4-(4-aminophenoxy)phenyl]sulfone (8.0 grams, 18.5 mmol),and cyclohexylamine (0.399 grams, 4.0 mmol) were dissolved inN-methyl-2-pyrrolidone up to a final concentration of 10 wt. %. Thesolution was allowed to stir at room temperature under an inertatmosphere for 12 hours. Xylene (12.0 grams) was added to the resultingamic-acid solution in order to form an azeotropic solution to removewater during imidization, which was carried out by heating the solutionto 180° C. for additional 12 hours. The resulting imide solutions werespin coated at 1,500 rpm at 60 seconds to form void free homogeneousfilms.

Example 17Bisphenol-A-Dianhydride-co-2,4,6-Trimethyl-m-Phenylenediamine-co-2-Methyl-1,5-PentanediamineOligomers End-Terminated with 2,6-Dimethyl Aniline

In this Example, 4,4′-Bisphenol-A-dianhydride (20.0 grams, 38.43 mmol),2,4,6-trimethyl-m-phenylene diamine (0.811 grams, 5.40 mmol),2-Methyl-1,5-Pentanediamine (commercially available from Invista undertrade name of Dytek-A, 3.556 grams, 30.60 mmol), and 2,6-dimethylaniline (0.609 grams, 5.03 mmol) were dissolved inN-methyl-2-pyrrolidone up to a final concentration of 10 wt. %. Thesolution was allowed to stir at room temperature under an inertatmosphere for 12 hours. Xylene (16.6 grams) was added to the resultingamic-acid solution in order to form an azeotropic solution to removewater during imidization, which was carried out by heating the solutionto 180° C. for an additional 12 hours. The resulting imide solutionswere spin coated at 1,500 rpm at 60 seconds to form void-free,homogeneous films.

Example 18 Bisphenol-A-Dianhydride-co-3,3′-DiaminodiphenylSulfone-co-2-Methyl-1,5-Pentanediamine Oligomers End-Terminated withCyclohexylamine

In this procedure, 4,4′-Bisphenol-A-dianhydride (10.0 grams, 19.2 mmol),3,3′-diaminodiphenyl sulfone (2.220 grams, 8.9 mmol),2-Methyl-1,5-Pentanediamine (commercially available from Invista undertrade name of Dytek-A, 1.039 grams, 8.9 mmol), and cyclohexylamine(0.273 grams, 2.8 mmol) were dissolved in N-methyl-2-pyrrolidone up to afinal concentration of 10 wt. %. The solution was allowed to stir atroom temperature under an inert atmosphere for 12 hours. Xylene (9.0grams) was added to the resulting amic-acid solution in order to form anazeotropic solution to remove water during imidization, carried out byheating the solution to 180° C. for additional 12 hours. The resultingimide solutions were spin coated at 1,500 rpm at 60 seconds to formvoid-free, homogeneous films.

Example 19Bisphenol-A-Dianhydride-co-2,4,6-Trimethyl-m-Phenylenediamine-co-1,2-DiaminocyclohexaneOligomers End-Terminated with Cyclohexylamine

In this Example, 4,4′-Bisphenol-A-dianhydride (10.0 grams, 19.2 mmol),2,4,6-trimethyl-m-phenylenediamine (0.663 grams, 4.42 mmol),1,2-diaminocyclohexane (1.514 grams, 13.26 mmol), and cyclohexylamine(0.317 grams, 3.2 mmol) were dissolved in N-methyl-2-pyrrolidone up to afinal concentration of 10 wt. %. The solution was allowed to stir atroom temperature under an inert atmosphere for 12 hours. Xylene (8.3grams) was added to the resulting amic-acid solution in order to form anazeotropic solution to remove water during imidization, carried out byheating the solution to 180° C. for an additional 12 hours. Theresulting imide solutions were spin coated at 1,500 rpm for 60 secondsto form void-free, homogeneous films.

Example 20Bisphenol-A-Dianhydride-co-2,4,6-Trimethyl-m-Phenylenediamine-co-4,4′-Methylene-Bis-CyclohexylamineOligomers End-Terminated with Cyclohexylamine

In this procedure, 4,4′-Bisphenol-A-dianhydride (10.0 grams, 19.2 mmol),2,4,6-trimethyl-m-phenylenediamine (0.657 grams, 4.38 mmol),4,4′-methylene-bis-cyclohexylamine (2.762 grams, 13.13 mmol), andcyclohexylamine (0.355 grams, 3.58 mmol) were dissolved inN-methyl-2-pyrrolidone up to a final concentration of 10 wt. %. Thesolution was allowed to stir at room temperature under an inertatmosphere for 12 hours. Xylene (9.2 grams) was added to the resultingamic-acid solution in order to form an azeotropic solution to removewater during imidization, which was carried out by heating the solutionto 180° C. for an additional 12 hours. The resulting imide solutionswere spin coated at 1,500 rpm for 60 seconds to form void-free,homogeneous films.

Example 21

The viscosity, softening point, and T_(g) of the compositions ofExamples 15, 16, 19, and 20 are reported in Table 4, while the values ofthe compositions of Examples 17-18 are reported in Table 5. Furtherstudies on thermal stability and chemical resistance were carried out onthese compositions. All of these compositions possessed the requiredthermal stability of at least up to 350° C. and exhibited minimalout-gassing (<0.5 wt. %).

TABLE 4 Properties of Examples 15-16 and 19-20 Weight Loss MolecularVISCOSITY Softening Temperature (Isothermal at Weight (Mn, T_(g) EXAMPLE(Pa · S, 350° C.) (in ° C. at 3,000 Pa · S) 350° C. for 4 hrs) Daltons)(° C.) 15 4.943 240 1.420% 3,940 176 16 169.6 299 0.1740%  19,800 207 190.796 239 3.173% 4,780 185 20 29.47 273 0.866% 9,810 202

TABLE 5 Properties of Examples 17-18 Weight Loss Molecular VISCOSITYSoftening Temperature (Isothermal at Weight (Mn, T_(g) EXAMPLE (Pa · S,300° C.) (in ° C. at 3,000 Pa · S) 300° C. for 4 hrs) Daltons) (° C.) 1722.52 214 0.6721% 12,700 144 18 4.451 208  1.557% 5,870 150

1. A wafer bonding method comprising: providing a stack comprising first and second substrates bonded together via a bonding composition layer comprising a compound; subjecting said stack to a temperature sufficient to soften said bonding layer; and separating said first and second substrates, wherein said compound is selected from the group consisting of polymers and oligomers having a formula selected from the group consisting of

wherein R is selected from the group consisting of

wherein R is selected from the group consisting of alkyl-substiteted phenyls

 and X is selected from the group consisting of phenyl sulfones, aromatics, aliphatic, and cyclic aliphatics; and

wherein Z is selected from the group consisting of siloxanes and moieties comprising ether bridges, and wherein said compound further comprises an endcap group derived from a compound selected from the group consisting of aromatic mono-amines, aliphatic mono-amines, cyclo-aliphatic mono-amines, and phthalic anhydrides.
 2. The method of claim 1, wherein said temperature is at least about 200° C.
 3. The method of claim 1, wherein said separating comprises applying a force to at least one of said first and second substrates while causing the other of said first and second substrates to resist said force, said force being applied in a sufficient amount so as to separate said first and second substrates.
 4. The method of claim 3, said stack having an axis that passes through both the first and second substrates, said force being applied in a generally transverse direction relative to said axis.
 5. The method of claim 3, said applying a force comprising lifting the at least one first and second substrate in a direction generally away from the other of said first and second substrates.
 6. The method of claim 1, further comprising thinning one of said substrates prior to said subjecting.
 7. The method of claim 1, further comprising subjecting said stack to a process selected from the group consisting of backgrinding, metallizing, patterning, and combinations thereof prior to said subjecting to a temperature.
 8. The method of claim 1, wherein said providing a stack comprises: applying a bonding composition to at least one of the first and second substrates; and contacting the substrates with one another so as to bond the substrates together.
 9. The method of claim 8, wherein said applying comprises spin-coating the bonding composition onto one of the first and second substrates.
 10. The method of claim 8, wherein said contacting comprises applying pressure to the substrates.
 11. The method of claim 1, wherein: said first substrate has a first surface and a second surface remote from said first surface and comprising at least one active site and plurality of topographical features, and said bonding composition layer is bonded to said second surface; and said second substrate comprises a bonding surface that is bonded to said bonding composition layer.
 12. The method of claim 11, wherein: said topographical features present respective end surfaces remote from the first surface of said first substrate, and at least one of the end surfaces is further from the first surface of the first substrate than the other of said end surfaces, said further end surface defining a plane that is substantially parallel to said first surface; and the distance from said plane to the bonding surface on said second substrate varying by less than about 10% across said plane and second substrate bonding surface.
 13. The method of claim 1, wherein said first substrate: has a first surface and a second surface remote from said first surface; comprises at least one active site and plurality of topographical features on said second surface; and is selected from the group consisting of microelectromechanical system devices, display devices, flexible substrates, compound semiconductors, low k dielectric layers, dielectric layers, ion implant layers, and substrates comprising silicon, aluminum, tungsten, tungsten silicide, gallium arsenide, germanium, tantalum, tantalum nitrite, SiGe, and mixtures of the foregoing.
 14. The method of claim 1, wherein said second substrate comprises a material selected from the group consisting of sapphire, ceramic, glass, quartz, aluminum, and silicon.
 15. The method of claim 1, wherein said compound is (I), and X is selected from the group consisting of alkyl-substituted phenyls, isopropylidenediphenyl, and hexafluoroisopropylidene.
 16. The method of claim 1, wherein said endcap group is selected from the group consisting of alkyls,

where: R₄ is an alkyl; R₅ is a cyclic aliphatic group; and k is 0 to
 20. 17. The method of claim 1, wherein said compound is (II), and Z is a siloxane having the formula

where: each R³ is individually selected from the group consisting of hydrogen, alkyls, and phenyls; m is 1 to 6; and p is 1 to
 50. 18. The method of claim 1, wherein said compound is (II), and Z is a moiety comprising an ether bridge selected from the group consisting of 